The preferred embodiment concerns a printing system and a method for handling unfused pages in such a printing system.
The preferred embodiment in particular concerns an electrographic printing system in which images are applied on a recording medium by means of toner via an electrophotographic method, for example, and subsequently are fused on the recording medium with a fusing method (for example by means of radiant heat).
The preferred embodiment furthermore in particular concerns a printing system in which band-shaped recording media are printed in which, for example, paper webs that are wound on rolls are supplied to the printing system. Such systems are typically used in high capacity digital printing systems that print individual pages with print speeds of a few tens to a few thousands of DIN A4 pages per minute.
At such high speeds, problems sometimes occur when the running print operation is halted manually by an operator or is stopped automatically due to an internal system problem. In particular, given the execution of very large print jobs that, for example, comprise multiple hundreds of thousands or over a million pages, the problem can occur that page information is lost in the course of a printing stop, or already-printed pages or page portions are damaged such that they are no longer suitable to be issued. This problem can in particular occur given damages to the paper web. In such cases, a known possibility for error correction is to advance the paper web by a greater length so that all already-printed pages are issued and the printing process is then restarted. However, what is disadvantageous in this method is that the paper quantity that is advanced in this way is unprinted, and the corresponding paper quantity is to be discarded as spoilage.
Spoilage is also generated in many cases when it is required in the course of changing the printing apparatus over from a first print job to a second print job to vary certain apparatus parameters (for example a set page length), in particular when the transport of the recording medium is monitored inside the machine per page with sensors.
An electrographic printing system is known from US 2006/0147232 A1. An electrographic printing system in which recurring markers on a recording medium are scanned and detected is known from U.S. Pat. No. 6,256,474 B1.
Methods and devices with which error states in the operation of printing or copying apparatuses can be dealt with are known from U.S. Pat. No. 6,666,594 B2 and US 2006/0153613 A1.
A printing system in which the execution of print jobs is tracked specific to the document and, in the case of an output error, a targeted reprinting of documents occurs is known from US 2004/0139115 A1.
The aforementioned documents are herewith incorporated by reference into the present Specification.
As already mentioned above, upon termination of a printing process in which printing occurs on web-shaped recording material the problem sometimes exists that spoilage is generated. In printing systems in which the print image is applied on the recording material in a transfer printing station such that the print image is not yet permanently adhered to the recording medium (consequently is not yet fused), is subsequently to be transported over a certain transport distance and only then arrives at a fixing station within which the print image is fused on the recording material, unwanted large quantities of spoilage can be generated in the cited cases because the transport distance between the transfer printing station and the point at which the fused image leaves the printing apparatus is relatively long and, for example, can amount to multiple meters. For this reason it is desirable to initially leave printed, but not fused, pages in the printing apparatus in the course of a printing stop or a change of print jobs and apparatus change-over's connected with these. On the other hand, however, in many cases it is necessary to move the paper web at least partially in the course of such change-over's in order to be able to make necessary adjustments, for example the sensitization of sensors for the synchronization of the paper transport.
Since, in the course of apparatus stops or change-over measures, diverse apparatus groups are placed in separate operating states or are even deactivated, the danger exists that pages that have already been printed ultimately are not fused, meaning that they leave the printing apparatus unfused and therefore are unusable. In later processing steps this can even lead to contamination or disruptions in other apparatuses because the unfused dye (for example toner) unintentionally detaches from the recording medium.
If such unfused pages are output, it is additionally disadvantageous that the page ultimately loses its information, i.e. is unusable. In particular given a processing of documents that is automatic to the greatest possible extent, for example given the automatic generation of invoices in computers and their printing up to the point of mailing to the invoice recipients, this can undesirably have the result that unfused pages are delivered and the printed information does not reach the recipient.